Set Appliance State:

Gas Off
Isolate Mains Power to appliance as per TOPs P4
Attach gauge to inlet pressure test point
Gas On

Observation:

Whilst pressing the ON button, measure the working gas pressure at the inlet pressure test point (1).
Is there a satisfactory inlet pressure?
Note:
When pressure gauge is removed the pressure test point should be tightened and checked for gas tightness.